162 — Natural History of the Farallones. [ZOE 
siderable convenience in the social intercourse of the parent birds. 
It is a significant fact that the patch is white, as with the markings 
about the head in so many mammals that live in burrows. There 
is, however, another use in this white patch of the sea parrot. I | 
noticed that the setting bird always faced the entrance to her re- 
treat, exposing the white patch in full view. On seeing this special 
precautions were used in inserting the hand to prevent being bitten, 
for the bite of a puffin is a dangerous thing. It is quite evident that 
this white patch must serve as a warning for intruders to keep off, 
and is one of the few cases of warning colors among birds which 
have come to my notice. 
A series of the young of Cassin’s auklet was obtained, but the 
bird is nocturnal in habits so. that very little was seen of the adult. — 
Figure 3 of Plate xxi shows the young puffin’s head, the bill, even 
at this early stage of development being greatly enlarged and trans- 
versely grooved. The bird is feathered when hatched, apparently, 
at least the youngest specimen obtained was completely so, and of 
a dark brown color. Figure 5 shows the head of Cassin’s auklet. 
it may be recognized at the earliest age obtainable by the little up- 
turned snub bill and the gray feet. 
In size and general color the young of the pigeon guillemot is 
not unlike the young of Cassin’s auklet, both being dark-brown in 
color; but the difference in the shape of the bill, as shown in Fig- 
ure 4 of Plate xxi, is very marked, as is also the character of the 
feet. The throat of the guillemot is feathered, while in the auklet 
— it is almost naked, and of a dark slaty color. 
~ Mr. Anthony noticed Cassin’s auklets nesting along the sides of 
one of the caves which he explored, which is quite an unusual habit 
with this species. I noticed that they also nest on level ground in 
crannies under loose rocks. At night, especially if the moon is up, 
the birds are very abundant and noisy. Their note resembles the 
creeking of a rusty gate, and may be represented by the syllables 
creek a reek! creek a reek! creek a reek! Another nocturnal bird is 
the ashy petrel ( Oceanodroma homochroa). It is perhaps not so rare 
upon the island as it. is difficult to find. Mr. Anthony obtained a 
large number of eggs and birds by systematically turning over rocks 
ona hillside where they were known to be found. The nest is fre- 
quently, though by no means invariably, indicated by the strong 
_ musky odor in its vicinity. The flight of the petrel was light, quick 
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